Another day, another captain's innings. Graeme Smith's century on the second afternoon in Adelaide might not have had the elegance of Michael Clarke's double-hundred on day one, but it was no less important for his side. After Australia piled on 550 in less than four sessions, South Africa needed somebody from their top order to anchor a hefty reply. That man was Smith, who finished the day unbeaten on 111, having had support from Alviro Petersen in a 138-run opening stand.

South Africa did not bat with the carefree attitude that the Australians did on Thursday, scoring at 3.23 runs per over. But that was only natural. When the opposition has such an enormous headstart, a certain amount of vigilance is required to ensure the situation does not become diabolical. The boundaries might be expected to flow more freely on the third day, if they again start solidly. They will begin on 2 for 217, with Jacques Rudolph on 25 alongside Smith.

It was a day on which the Australians discovered that the benign Adelaide Oval pitch that had been their friend over the first four sessions could just as easily become an enemy. Morne Morkel found something from the surface in the opening session, completing his first five-wicket haul against Australia to make sure South Africa would not spend another full day in the sun. Australia's bowlers toiled for little reward.

It took a run-out to break the opening partnership. On 54, Petersen pushed the ball to mid-on and set off for a run, but found himself on a collision course with his partner Smith. After taking a wide berth to get around his captain, Petersen compounded the problem by not sliding his bat in his reach for the crease, although it may not have saved him from Michael Hussey's direct hit in any case.

The only breakthrough made by an Australian bowler came through the occasional legspin of David Warner, who lured Hashim Amla (11) out of his crease. Amla played the wrong line and despite the wicketkeeper Matthew Wade struggling to grasp the ball cleanly at first, was so far down the pitch that he couldn't get back in time to avoid being stumped.

It wasn't Wade's first shaky moment. On 46, Smith, who has never been stumped in a Test career spanning 182 innings, advanced down the pitch and tried to flick Michael Clarke through leg and when he missed, Wade, who appeared to have lost sight of the ball, fumbled and lost the chance to take the bails off.

The Australians also thought they had Smith caught behind on 78, when James Pattinson came around the wicket and nipped a ball away off the seam. Smith dabbed at the ball and was given out caught behind, but when he asked for a review, there was no evidence from Hot Spot that his bat had touched the ball and the decision was overturned. They were important moments for Smith, just as Clarke had had some close calls in his innings.

Otherwise, Smith played well, leaving the ball and waiting for those he could dispatch or work through the gaps. He brought up his century from his 198th delivery, with a cut behind point for four off the bowling of Nathan Lyon, and it was typical of his innings - wait for the bad ball. Smith battled what appeared to be cramp during his innings but he should return fresher on the third day, and notably for South Africa, the team has never lost a Test in which Smith has scored a hundred.

They can also take heart from the fact that twice in the past decade, a team has lost having posted a 550-plus total batting first at Adelaide Oval - something that outside Adelaide has only happened once in Test history. South Africa's chances of victory might be slim, and not helped by the fact that Jacques Kallis has a hamstring injury and will struggle when he bats, but they know Adelaide can provide them with as many runs as it did Australia.

The Australians added 68 to their overnight score for the loss of their last five wickets and the majority of their runs came from the No.9, Pattinson, who played some impressive strokes in reaching his best first-class score of 42. He crunched Dale Steyn for a pair of boundaries through the off side and cleared the rope twice off Imran Tahir before he was the last man out, edging Steyn to Smith at slip.

The day had started on a positive note for South Africa when Morkel bowled Clarke, who added only six to his overnight score and was dismissed for 230. The rewards kept coming for the hard-working Morkel when he had Wade caught behind for 6, trying to drive a delivery that angled across him, and his five-wicket haul arrived when Ben Hilfenhaus hooked a short ball and was caught at fine leg for a duck.

Morkel's previous best in an innings against Australia was three wickets, and he finished up with 5 for 146 from 30 overs, his workload having increased significantly due to Kallis being unavailable. There was also a moment of relief and joy for Rory Kleinveldt, who claimed his first Test wicket when he had Peter Siddle caught at slip for 6. The umpire called for a replay to check that Kleinveldt, a serial no-baller, had not over-stepped, and by a matter of millimetres his wicket stood.

It was all part of a much more pleasant day for South Africa than day one.

Brydon Coverdale is an assistant editor at ESPNcricinfo. He tweets here

After enduring a tricky start to his Manchester United career, perhaps it is fair that Marcos Rojo celebrated so boisterously as he watched his first professional club Estudiantes beat fierce rivals Gimnasia